add iso date template filter.

improve template errors when something is wrong.

improve templating. allow {foo} as well as #foo#. add new functions for changeset authors.

move shortuser into util module.

make parsestring work with strings that do not have quotes.

use safer string parser for template engine.

move repeated work out of inner loops.

many small changes to templater. get string code to parse escapes. uses eval now, should parse strings itself soon. let caller check if fragment is defined using "in". make templatepath take optional file name.